Process for producing electric coils



March 25, 1930. M. BARNUM I PROCESS FOR PRODUCING ELECTRIC COILS Filed Oct. 11, 1929 Patented Mar. 25, 1930 UNITED STATES PATENT OFFICE MARSHALL BABNUH, OF NEW HAVEN, CONNECTICUT, ASSIGNOB TO THE ACME WIRE COHI'ANY, NEW HAVEN, CONNECTICUT, A CORPORATION PROCESS FOR PRODUCING ELECTRIC COILS Application filed October 11, 1929. Serial No. 398,873.

This invention relates to an improvement in processes or methods for producing electric coils and particularly electric coils which are '1 speak, the various convolutions of the wire and the core-tube into a homogeneous whole.

One of the main objections to treating electric coils with liquids which are heated to increase their penetrative action, desirable though this is, is the fact that such treatment tends to soften the absorbent paper or other fibrous core and thus permit the same, together with the convolutions of wire wound thereon, to twist, warp, or otherwise become distorted from a predetermined form.

The object of this invention is to provide a method for the manufacture of electric coils of the type having tubular cores of absorbent fibrous material which will minimize warping and distortion and result in the production of uniform and workmanlike articles.

With the foregoing and other objects in view, my invention consists in a process for the manufacture of electric coils having certain novel features as will be hereinafter described and particularly recited in the claims.

In the accompanying drawings:

Fig. 1 is a perspective view of one of the many forms of electric coils which may be manufactured by means of my improved F1 2 1s a broken perspectlve new of a I T1 of core-tube prior to the indurating treatment thereof for rendering the same impervious to hot impregnating liquids;

Fig. 3 is a corresponding view of the same after indurating treatment;

Fig. 4 is a. perspective View of a short section of core-tube suitable for employment in the type of coil shown in Fig. 1 and indicated by stippling as indurated prior to the wimling of the convolutions of wire thereon; and

Fig. 5 is a perspective view of an electric coil in the stage of its manufacture just prior to its treatment with a hot in'ipregnating liquid, a portion of the paper insulation being broken away to expose the wire.

In carrying out my invention I apply to a length of core-tube 10, in any approved manner, treatment or coating 11, indicated by fine properties, and by the use of suc 1 term I wish to be understood as meaning its capacity for rendering the object treated effectively resistant to the softening or other deleterious effects of hot impregnating compounds, such as wax, resin, or pitch.

Many difierent substances may be employed as an indurating liquid, within the meaning of that term as herein employed, to impart to the fibrous core-tube the resistant properties above described. I have found, howeve", sodium sicilate to be a desirable indurating substance for the reason that it is both lo w in cost and effective for the purpose intended. Other fluids have, however, proven satisfactory, such, for instance, as shellac, and numerous salts, which contain water of crystallization, so that when the latter is once evaporated, the core-tube is both stiff and resistant to hot impregnating fluids.

. Preferably, I treat a length of core-tube 10, prior to severing it into the shorter corepieces 12 (Fig. 4), though it is obvious that the individual core-pieces may be treated, if desired.

After the core-tube has been treated either in long lengths or individually to render it substantially impervious to hot impregnating liquids or compounds, a coil of wire 13 is wound thereon in any approved manner, together with a strip 14 of paper which is designed to be interposed between each layer of wire in accordance with usual practice. The resultant article has now assumed the form shown in Fig. 5.

The next important step in carrying out my invention consists in treating the unit In testimony whereof, I Have signed this specification.

MARSHALL BARNUM.

comprising the coil of wire 13, paper strip v 14 and core-tube 12 with an impregnating fluid of wax resin, pitch, etc., which is applied hot to better cause it to penetrate into the paper 14 and all interstices in the coilstructure.

The impregnating fluid is preferably ap-.

plied to the coil-structure by immersing the latter in a molten and highly-fluid bath of the desired constituents though, as is obvious, other methods of application may be employeda When the hot impregnating fluid is applied to the coil-structure as above described, the same is prevented from so deleteriously affecting the core-tube 12, which is virtually the foundation of the coil, as to soften or weaken it to thereby permit distortion.

As a result of the employment of my improved process electric coils may be produced which do not vary in size or form from a predetermined standard and therefore may be relied upon to fit into an assembly such as radio-receivers, etc., without alteration.

I claim:

1. A process for the manufacture of electric coils of the type comprising a fibrous absorbent core-tube and a coil of wire there on, consisting in treating the core-tube prior to the winding of the wire thereon with a liquid having the characteristic, when solidifled, of being substantially impervious to hot impregnating liquids, thereafter winding a coil of wire upon the core-tube so previously treated and then treating the core-tube and coil as a unit with ahot impregnating liquid; whereby during the latter treatment, the 'said core-tube is shielded from the softening and weakening efiects of the hot impregnating liquid and the distortion of the unit avoided.

2; A process for the manufacture of electric coils of the type comprising a fibrous absorbent core-tube and a coil of wire thereon,

consisting in treating the core-tube prior to the winding of the Wire thereon with a liquid having the characteristics, when solidified, of being substantially impervious to hot impregnating liquids and physically hard, thereafter windingsa coil of wire upon the 

